Image display

ABSTRACT

A technology effective for improving the luminous efficiency, lifetime, and color temperature of a PDP having phosphor layers of three colors is disclosed. A PDP comprises a plurality of narrow tubes ( 60 ) arrayed on a substrate ( 51 ). In each narrow tube ( 60 ), one of phosphor layers ( 61 R;  61 B,  61 G) is formed and a discharge gas is contained. The compositions and pressures of the discharge gases are set within appropriate ranges respectively corresponding to the phosphor layers ( 61 R,  61 B,  61 G). Consequently, the PDP can have a lengthened life-time and an improved luminous efficiency. Reductions of variation in breakdown voltage and adjustment of color temperature are also possible with this constitution.

TECHNICAL FIELD

The present invention relates to image display devices such as plasmadisplay panel displays and a manufacturing method for such image displaydevices that display images by using phosphor layers of different colorsto convert ultraviolet light, generated as discharge occurs, intovisible light.

BACKGROUND ART

In recent years, hopes for high definition, large screen televisionssuch as-Hi Vision have been high and getting higher. In each of thefields of CRT, Liquid crystal displays, and Plasma Display Panels(hereafter referred to as PDP) progress has been made.

Of the above technologies, PDP in particular makes it possible toachieve a large screen with a small depth, and products in the 60-inchclass have already been developed.

PDPs can be broadly divided into two types, Direct Current type (DCtype) and Alternating Current type (AC type), but currently, the ACtype, appropriate for increasingly large devices, is more common.

A typical AC panel discharge type PDP is constructed with a back glasspanel and a front glass panel disposed opposite one another such that aspace is formed between the panels. In order to form a gas dischargespace, the periphery (not shown in the drawings) is sealed using asealing material composed of a glass with a low melting point. Then, aninert gas (for example a mixture of He and Xe) at a pressure ofsubstantially 300 Torr to 500 Torr (40-66.5 kPa) is enclosed in thespace between the two plates.

Discharge electrodes are disposed in a stripe pattern on the front glasspanel, and this arrangement is overlaid with a dielectric layer composedof a dielectric glass and a protective layer composed of Magnesium Oxide(MgO).

Address electrodes are disposed in a stripe pattern on the back glasspanel, and a visible light reflective layer is provided so as to coverthe address electrodes. On top of this arrangement, barrier ribs aredisposed between the address electrodes to divide the space describedabove, and a phosphor layer composed of red, green or blue ultravioletlight excited phosphor is provided in the gaps between the barrier ribs.

Also, as disclosed in Japanese laid open patent application number11-162358, a PDP having a plurality of hollow narrow tubes made of glassand arrayed on a substrate, red, green or blue phosphor layers appliedto the inside surfaces of the tubes, and a discharge gas enclosed withinthe tubes has also proposed. In a PDP using hollow narrow tubes in thisway there is no need to enclose the discharge gas between the two panelsbecause the discharge gas is enclosed in the hollow narrow tubes, andmanufacture of the PDP is therefore simplified. Also, since the hollownarrow tubes also serve as barrier ribs and the dielectric glass layer,the PDP may be lightened.

The PDP principle for light emission is basically the same as forfluorescent lighting: when an electric field is applied betweenelectrodes and a glow discharge is generated in the discharge space,short wavelength ultra-violet light emitted from a discharge gas inducesexcited emission in the red, green and blue phosphors. However, in thecase of a PDP, since the discharge energy to ultraviolet lightconversion efficiency and the ultraviolet light to visible lightconversion efficiency in the phosphor are low, it is difficult toachieve the high emission efficiency of fluorescent lighting.

There is, therefore, a desire for an improvement in the luminance andemission efficiency of a PDP.

Also, research aiming to provide a High Definition PDP's is in progress.

For example, research is also being carried out into the suppression ofdeterioration of the emission characteristics of the phosphor layers ina PDP.

Also, to provide a High Definition PDP, it is also important that thecolor temperature when white is displayed is raised by adjusting thecolor of each colored cell.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an effective technologyto improve characteristics such as the lifetime, the luminous efficiencyand the color temperature of an image display apparatus such as a PDP,which displays an image by converting ultraviolet light, generated asdischarge occurs, into visible light via phosphor layers of variouscolors.

To achieve this object, the present invention is an image displayapparatus in which a plurality of narrow tubes are disposed so as toextend across a substrate, each narrow tube containing phosphor materialand enclosing discharge gas, the image display apparatus displaying animage by applying voltages to the narrow tubes so as to cause dischargesto occur therein, and converting ultraviolet light generated as thedischarges occur into visible light via the phosphor material, wherein,the plurality of narrow tubes include at least one first narrow tube andat least one second narrow tube, and the phosphor materials respectivelycontained in the first and second narrow tubes differ from each other,and the discharge gases respectively enclosed in the first and secondnarrow tubes differ from each other in at least one of composition andpressure.

It is preferable that the image display apparatus having the abovecharacteristics is manufactured using an image display apparatusmanufacturing method, the method including: a gas enclosing step ofenclosing discharge gas within a plurality of narrow tubes containingphosphor material; and a disposing step of disposing so as to extendacross a substrate the plurality of narrow tubes in which the dischargegas was enclosed in the enclosing step.

According to this manufacturing method, if the first narrow tubes thatcontain phosphor material, and the second narrow tubes, which containphosphor material that differs from the phosphor material contained inthe first narrow tubes, are provided, the discharge gas enclosed in thefirst narrow tube and the discharge gas enclosed in the second narrowtube can easily be made to differ from each other in at least one ofcomposition and pressure.

Since, in an image display apparatus such as a PDP, the phosphors areusually provided in three colors (red, green and blue), the phosphormaterial contained in the first narrow tube may be of at least one colorselected from red, green and blue, and the phosphor material containedin the second narrow tube may be of at least one color other than the atleast one color selected for the phosphor contained in the first narrowtube.

The phosphor materials contained in the contained in the narrow tubesmay, for instance, be melted into glass that forms the narrow tubes orprovided on the inside surface of the narrow tubes.

In the image display apparatus, it is desirable that a plurality offirst electrodes are arrayed so as to extend in a length direction ofthe narrow tubes, and a plurality of second electrodes are arrayed so asto extend in a direction which intersects the length direction of thenarrow tubes such that an external driving circuit can apply a voltageto each narrow tube.

Here, to obtain a favorable discharge efficiency, it is desirable thatthe plurality of first electrodes are provided between the substrate andthe narrow tubes, and the plurality of second electrodes are attached tothe plurality of narrow tubes.

Also, it is also desirable that a layer composed of MgO is formed insideeach narrow tube.

Also, included in the present invention is an image display apparatus inwhich a pair of substrates are disposed opposite one another such thatan internal space is formed therebetween, electrodes and at least twotypes of phosphor layer are provided between the substrates, anddischarge gas is enclosed in the internal space, the image displayapparatus displaying an image by applying voltages to the electrodes soas to cause discharges to occur in the internal space, and via thephosphor material, converting ultraviolet light generated as dischargesoccur into visible light, wherein, the internal space is divided into afirst space provided with a first phosphor layer and a second spaceprovided with a second phosphor layer, and the discharge gasesrespectively enclosed in the first and second spaces differ from eachother in at least one of composition and pressure.

It is preferable that the image display apparatus of the type describedabove is manufactured using an image display apparatus manufacturingmethod including: an outer vessel forming step of forming an outervessel in which pair of substrates are disposed opposite one anothersuch that an internal space is formed therebetween, electrodes and atleast two types of phosphor layer are provided between the substrates,and discharge gas is enclosed in the internal space, the internal spaceis divided into a first space provided with a first phosphor layer and asecond space provided with a second phosphor layer, and first and secondexhaust tubes connecting to the first and second spaces respectively areprovided; and an exhausting-enclosing step of, via the first and secondexhaust tubes respectively, exhausting the first and second spaces andenclosing discharge gas therein.

Since, in an image display apparatus such as a PDP, the phosphors areusually provided in three colors (red, green and blue) the firstphosphor layer may be of at least one color selected from red, green andblue, and the second phosphor layer may be of at least one color otherthan the at least one color selected for the first phosphor layer.

Usually, for an image display device such as the one described above, ifthe internal space is partitioned into a plurality of spaces by aplurality of barrier ribs provided in a stripe pattern, and each grooveformed between the plurality of barrier ribs is closed at one end, thedivision of the internal space into a first space and a second space caneasily be achieved.

As well as noting that the luminous efficiency and the effect on factorssuch as the discharge voltage are different for each type of phosphor,the inventors looked at the effect of the composition and pressure ofthe discharge gases on factors such as the luminous efficiency,discharge voltage, and emission color.

Specifically, points 1-4 are notable.

1. The effect on the discharge voltage is different depending on thetype of phosphor layer provided in a discharge cell. On the other hand,the discharge voltage is also affected by the composition and pressureof the discharge gas.

2. The efficiency of the conversion from ultraviolet light to visiblelight is different depending on the type of phosphor layer. On the otherhand, the luminous efficiency differs according to the composition andpressure of the discharge gas.

3. The color of the emission from a discharge cell is affected not onlyby the type of phosphor layer, but also by the composition and pressureof the discharge gas.

4. The composition and pressure conditions of the discharge gas thatinfluence characteristics such as the lifetime of the phosphor layersdiffer for each type of phosphor.

Based on this knowledge, the present invention has made it possible toimprove characteristics such as the lifetime of the phosphor layers, toadjust the emission luminance for each color, and to suppress variationin the discharge voltage between the spaces where the phosphor layers ofthe various colors are provided. These effects are achieved by varyingthe composition and pressure conditions of the discharge gas (by fixingthe composition and pressure of each discharge gas separately) for eachtype of phosphor layer.

Thus, since the appropriate ranges of pressure and composition for asuitable discharge gas to allow each type of phosphor layer to achieve along lifetime are often different as described above, if the pressureand composition of the discharge gas are substantially the samethroughout the image display apparatus, it is not possible to set adischarge gas pressure and composition that is optimum for all thephosphors. Also, since the effect of each color of phosphor on thedischarge starting voltage is different, if the pressure and compositionof the discharge gas are substantially the same throughout the imagedisplay apparatus, the discharge starting voltage be caused to varydepending on the color of each phosphor. Also, if the pressure andcomposition of the discharge gas are substantially the same throughoutthe image display apparatus, the effect of discharge gas on the color ofemission from the phosphors of each color is uniform. It is not,therefore, possible to separately adjust the emission color of eachphosphor using the discharge gas, and hence, it is difficult to adjustthe color temperature when white is displayed.

According to the present invention, however, since at least one of thecomposition and the pressure of the discharge gas may be varied betweenthe first narrow tubes and the second narrow tubes (or a between a firstspace and a second space), at least one of the composition and thepressure of the discharge gas can be adjusted to fit the characteristicsof the phosphor material (phosphor layer) included in each narrow tube(or each space).

For example, a composition and pressure of the discharge gas suitablefor a long lifetime for the phosphor material (phosphor layer) includedin each narrow tube (or each space) can be fixed. Also, even if thephosphor included in each narrow tube (or space) affects the dischargestarting voltage differently, variation in the discharge startingvoltage can be suppressed by adjusting the composition and pressure ofthe discharge gas in each narrow tube (or each space). Also, since theemission color from the phosphor included in each narrow tube (or ineach space) can be adjusted separately via the discharge gas, the colortemperature when white is displayed can be simply adjusted.

Hence, according to the present invention a High Definition imagedisplay device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of part of a PDP of a First Embodiment;

FIG. 2 is a schematic cross-section of a PDP sectioned parallel to thebarrier ribs;

FIG. 3 is a cross-section of the PDP sectioned perpendicular to thebarrier ribs;

FIG. 4 is a perspective view of a PDP of a Second Embodiment; and

FIGS. 5A, 5B and 5C describe the manufacturing process for a PDP.

BEST MODE FOR CARRYING OUT THE INVENTION

The following describes embodiments of the present invention.

First Embodiment

(Overall Construction of a PDP)

FIG. 1. is a perspective view of part of a PDP of the Embodiment 1.

The PDP of this embodiment is constructed as follows. A front glasspanel 10 and a back glass panel 20 are disposed opposite one another. Inorder to form a space 30 for a gas discharge, the periphery is sealedusing a sealing material 40 (omitted from FIG. 1; refer to FIG. 2)composed of a glass with a low melting point. An inert gas (for examplea mixture of He and Xe or a mixture of Ne and Xe) at a pressure ofsubstantially 300 Torr to 500 Torr (40-66.5 kPa) is enclosed in thespace 30 between the two plates.

To form the front panel 10, a plurality of pairs of discharge electrodes12 a and 12 b are arrayed in a stripe pattern on the facing surface ofthe front substrate 11 (i.e. the surface that faces the back panel).This arrangement is overlaid with a dielectric layer 13 composed of adielectric glass, and a protective layer 14 composed of MgO. Theprotective layer 14 is formed using a vacuum deposition method or thelike.

To construct the back panel 20, a plurality of data electrodes 22 aredisposed in a stripe pattern on the facing surface of the back substrate21 (i.e. the surface facing the front panel). A visible-light reflectivelayer 23 is provided so as to cover this arrangement. On top of thereflective layer 23, barrier ribs 24 are formed in a stripe pattern todivide the space 30, and phosphor layers 25R, 25G and 25B composed ofred, green and blue ultraviolet excited phosphors are provided in thegaps (grooves 26) between the barrier ribs 24.

Examples of some possible colored phosphors include Y₂O₃:Eu for a redphosphor, ZnSiO₄:Mn for a green phosphor and BaMgAl₁₀O₁₇:Eu for aphosphor.

In a PDP of the above construction, discharge cell is formed at eachpoint where the discharge electrodes 12 a and 12 b and the dataelectrodes 22 cross, and the external driving circuit applies a writevoltage between the data electrodes 2-2 and the discharge electrodes 12a and applies a sustain voltage between electrodes 12 a and 12 b. Thiscauses discharge in the discharge cells that were written to, and lightof the corresponding color is emitted from the phosphor layers 25R, 25Gand 25B.

Characteristics and Effects of a PDP According to the Present Embodiment

FIG. 2. is a schematic cross-section of a PDP sectioned parallel to thebarrier ribs. FIG. 3. is a cross-section of the PDP sectionedperpendicular to the barrier ribs

Grooves 26 are formed between the barrier ribs 24 and phosphor layers25R, 25G and 25B are formed in respective grooves 26 as shown in FIG. 2.

Of the two end parts of each groove 26, one or the other is closed withan auxiliary barrier rib, dividing the internal space 30 into a firstspace A and a second space B. Here, the three colored phosphor layers25R, 25B, 25G are divided such that two colored phosphor layers areincluded in the first space A, and the remaining colored phosphor layeris included in the second space B.

Barrier ribs 24 and auxiliary barrier ribs 27 are formed from a materialthat has good sealing properties, and the upper part of each wall isjoined to the protective layer 14 (see FIG. 3). With this construction,the first space A and the second space B are sealed off from each other.

A discharge gas is enclosed in both the first space A and the secondspace B. However, in each space, one or both of the pressure and thecomposition of the discharge gas are adjusted to be within suitableranges to achieve some objective, the adjustments corresponding to thecharacteristics of the phosphor layer of the space in question.

For example, the composition and pressure of the discharge gas may beset with the objective of obtaining a high luminous efficiency and along lifetime.

Specifically, the suitable ranges for the composition and pressure ofthe discharge gas often differ for each discharge space in which aphosphor layer 25R, 25G, 25B is formed, in which case it is not possibleto fix the pressure and composition within ranges appropriate for eachcolor if the pressure and composition of the discharge gas are uniformacross the whole panel as for a conventional PDP. On the other hand, inthe present embodiment, a higher luminous efficiency and a longerlifetime can be obtained for the panel as a whole by setting thepressure and composition of the discharge gas within ranges suitable toobtain both a long life and high luminous efficiency in each phosphorlayer in space A and space B respectively.

Furthermore, the composition and pressure of the discharge gas may beset with the objective of adjusting the discharge starting voltage.

Specifically, since each color of phosphor layer affects the startingdischarge voltage differently, a variation in the discharge voltageoccurs when the pressure and composition of the discharge gas areuniform across the whole panel, as for a conventional PDP. In regard tothis problem, if the pressures and compositions are set separately forspace A and space B respectively as for the present embodiment, thedischarge starting voltage may also be adjusted via the discharge gaspressure and composition and, therefore, the variation in the dischargestarting voltage can be reduced in the panel as a whole.

Moreover, the composition and pressure of the discharge gas may be setwith the objective of adjusting the emission color.

Specifically, the emission color of each discharge cell is affected notonly by the phosphor layer, but also by the composition and pressure ofthe discharge gas. However, if the pressure and composition of thedischarge gas are uniform across the whole panel, as for a conventionalPDP, the emission color of the discharge cells cannot be adjusted viathe discharge gas for space A and space B respectively. In regard tothis problem, according to the present embodiment, the emission colorcan be adjusted via the discharge gases for the space A and the space Brespectively. This means that color temperature adjustment may easily beachieved.

When the discharge voltage, the emission temperature or the like isadjusted via the composition and pressure of the discharge gas,increasing the quantity of Ne contained in the space, increases redemission. Increasing the quantity of Xe contained in a space, on theother hand, increases the quantity of ultraviolet light, and causes thedischarge voltage to rise. Therefore, in general, it is preferable thatthe quantity of Ne is increased for the space including a red phosphorlayer, and reduced for the spaces including a green phosphor layer or ablue phosphor layer, especially for the space including a blue phosphorlayer, and He or Kr included instead. Also, when a space includes a bluephosphor layer, it is further preferable to increase the quantity of Xecontained, since an increase the luminous intensity of blue is generallydesirable.

In this way, according to the present embodiment, it is possible to havea PDP with a long life, a high color temperature and a low dischargevoltage variation between cells of each color. A reduction in thevariation of the discharge voltage between cells of each color has thebeneficial effect of reducing defective discharge when the PDP is beingdriven.

Note also that the composition and pressure of the discharge gas, andthe combination of the discharge gas and a particular type of phosphorlayer may also be set for another objective. Of course, it is possibleto vary only the compositions of the discharge gases in the first spaceA and the second space B, while keeping the enclosing pressuresconstant, to vary only the enclosing pressures while keeping thecompositions constant, or to vary both the compositions and theenclosing pressures.

The following is a description of an example of how to adjust thecomposition and pressure of a discharge gas.

EXAMPLE 1

In the example shown in FIG. 2 and FIG. 3, the grooves 26 in which a redphosphor layer 25R and a green phosphor layer 25G are formed are closedat one end (the lower part in FIG. 2) by the auxiliary barrier ribs 27,and the grooves 26 in which blue phosphor layers 25B are formed areclosed at the other end (the upper part in FIG. 2) by the auxiliarybarrier ribs 27. With this construction, the phosphor layers 25R and thephosphor layers 25G are included in the first space A and the phosphorlayers 25B are included in the second space B.

A mixed gas of He and Xe, a mixed gas of Ne and Xe and the like may beused as discharge gases. Here, in the first space, which includes thered phosphor layers 25R and the green phosphor layers 25G, the fractionof Xe contained in the discharge gas is set low (5% by volume), and inthe second space B, which includes the blue phosphor layer 25B, thefraction of Xe contained in the discharge gas is set high (10% byvolume). Further, the first space, which includes the red phosphor layer25R and the green phosphor layer 25G, is filled with the discharge gasat a pressure of 400 Torr (53.2 kPa), and the second space B, whichincludes the blue phosphor layer 25B, is filled with the discharge gasat a pressure of 500 Torr (66.5 kPa).

Thus, the quantity of Xe contained in the first space A is greater thanthe quantity contained in the second space B, and the amount ofultraviolet light irradiating the blue phosphor layer 25B can beincreased to be greater than for the red phosphor layer 25R and thegreen phosphor layer 25G. Thus, the amount of blue emission can beimproved and the color temperature when white is displayed can beincreased.

EXAMPLE 2

Here an example of settings for the compositions of the discharge gasesis described for the case where, unlike the example in FIG. 2, green andblue phosphor layers are provided in the first space A and red phosphorlayers are provided in the second space B.

In the first space A, which includes green phosphor layers and bluephosphor layers, a typical gas composition is used (for example, Xemaking up 5% by volume of a mixed gas of Ne and Xe), whilst in thesecond space B, which includes red phosphor layers, a gas compositionwith a greater quantity of Ne (for example, Xe making up 10% by volumeof a mixed gas of Ne and Xe) is used.

With these settings, in the first space A, a balance is establishedbetween discharge voltage and discharge efficiency by using the typicalgas composition ratio, and in the second space B, color purity anddischarge efficiency can be improved due to the extra red emissionbecause of the Ne supplementing the emission from the red phosphorlayers.

EXAMPLE 3

Here an example of possible pressure settings and compositions for thedischarge gases is described for the case that red and blue phosphorlayers are provided in the first space A and green phosphor layers areprovided in the second space B.

Though dependent to some extent on the materials chosen for thephosphors of each color, there is a tendency for variation in thedischarge voltage to occur between each color of discharge cell due to atendency for the discharge voltage of the discharge cells having greenphosphor layers to be lower than the discharge voltages for thedischarge cells having red phosphor layers and green phosphor layers.

For this kind of case, in the first space A, which includes red phosphorlayers and a blue phosphor layers, a regular gas composition (forexample, Xe making up 6% by volume of a mixed gas of Ne and Xe) and aregular pressure are set, while in the second space B, which includes agreen phosphor layer, a gas composition with a higher proportion of Xe(for example, Xe making up 10% by volume of a mixed gas of Ne and Xe),or a higher enclosing pressure, are set. With this construction, thedischarge voltages in the second space B are adjusted upwards and areduction in the variation of the discharge voltage is thereforepossible. Moreover, the quantity of ultraviolet light irradiating thegreen phosphor increases, and hence, the luminance of the green cellscan be increased while maintaining the color purity of the green cells.

(PDP Manufacturing Method)

Front Panel 10:

The electrodes 12 a and 12 b are formed by printing a silver pastephotosensitized with an organic vehicle onto the front surface ofsubstrate 11 using a photo-patterning method, and after drying, exposingthe electrode pattern using a photo mask, developing, and firing thearrangement.

Next, the dielectric layer 13 is formed by printing on a paste oflow-melting-point lead glass, and after drying, firing the arrangement.A protective layer composed of MgO is formed on top of the dielectriclayer 13 using an electron beam evaporation method.

Back Panel 20:

Next, data electrodes 22 are formed on the back substrate 21 bypatterning a thick film silver paste using a screen printing method, andfiring the arrangement.

Next, the visible light reflective layer 23 is formed by printing on aninsulating glass paste to cover the data electrodes 22 using a screenprinting method, and firing the arrangement.

Next, the barrier ribs 24 and the auxiliary barrier ribs 27 are producedby patterning a thick film silver paste using a screen printing methodand then firing the arrangement.

Then, the phosphor layers 25R, 25G, 25B are formed by patterningphosphor ink onto the inner surfaces of the grooves 26 formed betweenthe barrier ribs 24 using a screen printing method, and then firing thearrangement.

The Bonding of Front Panel 10 and Back Panel 20:

Front panel 10 and back panel 20 are put together using via a glass fritinserted between the outside edge parts of the two members. At thistime, the glass frit is also applied to top parts of barrier ribs 24 andauxiliary barrier ribs 27. Then, by bonding back panel 20 and frontpanel 10 by way of heat-softening the glass frit, an outer vessel iscreated. At this time, an exhaust tube 41, which connects to the firstspace A, and an exhaust tube 42, which connects to the second space B,are fitted.

In the outer vessel created in this way, two sealed partitioned spaces,the first space A and the second space B, are formed between the frontsubstrate 11 and the back substrate 21, the exhaust tube 41 connectingthe first space A to the outside, and the exhaust tube 42 connecting thesecond space B to the outside.

Exhaust and Gas Enclosing:

After exhausting the spaces through the exhaust tube 41 and the exhausttube 42, the discharge space A is filled with a discharge gas via theexhaust tube 41, the discharge space B is filled with a discharge gasvia the exhaust tube 42, and the exhaust tube 41 and the exhaust tube 42are then sealed.

Embodiment 2

(Overall Construction of a PDP)

FIG. 4 is a perspective view of the construction concept for a PDP of aSecond Embodiment.

To construct this PDP, narrow hollow tubes 60 containing red, green andblue phosphors and discharge gases are arrayed on a substrate 51 in thestated order, the discharge gases being enclosed within the hollowtubes, and at least one of the composition and pressure of each encloseddischarge gas being adjusted according to the type of phosphor.

Following is a description of the construction.

A plurality of ribs 53 and a plurality of data electrodes 52 are formedin stripe patterns respectively on a substrate 51, which is a platecomposed of either glass or plastic.

Grooves 54 are formed between the ribs 53, and the data electrodes 52extend along the bottom of these grooves. Then the plurality of narrowtubes 60 is arrayed so as to fit into the grooves 54.

On the internal surface of each narrow tube 60, a red phosphor layer61R, a green phosphor layer 61G or a blue phosphor layer 61B is providedon the substrate 51 side, an MgO layer is provided on the opposite side.

Though not shown in the drawings, both end parts of each narrow tube 60are sealed, and a discharge is gas enclosed within each narrow tube 60.

Joining layers 63, which fix neighboring narrow tubes 60 together, areprovided between the narrow tubes 60.

Furthermore, a plurality of discharge electrodes 71 a and 71 b isarrayed so as to span across the plurality of narrow tubes 60.

Note also that, though the forming of an MgO layer 62 is notindispensable, it is preferable because of the resulting improvement inthe discharge efficiency inside the narrow tubes when the PDP is driven.

In a PDP of the above construction, discharge cell is formed at eachpoint where the discharge electrodes 71 a and 71 b and the dataelectrodes 52 cross, and the external driving circuit applies a writevoltage between the data electrodes 52 and the discharge electrodes 71 aand applies a sustain voltage between electrodes 71 a and 72 b. Thiscauses discharge in the discharge cells that were written to, and lightof the corresponding color is emitted from the phosphor layers 61R, 61Gand 61B.

Characteristics and Effects of a PDP According to the Present Embodiment

In a PDP of the present embodiment, a phosphor layer 61R, 61G and 61B isenclosed together with a discharge gas in each narrow tube 60. Thus, inthe same way as described for the Embodiment 1 above, both the pressureand the composition of the discharge gas may be set separately toachieve some objective, the settings fitting the characteristics of thephosphor layers 61R, 61G and 61B.

Also, since the pressure and composition of the discharge gas can be setfor each narrow tube 60 individually, the pressure and composition ofthe discharge gas can be set more precisely within suitable ranges,compared with when the space is divided into two as in the FirstEmbodiment.

For example, the pressure and composition of the discharge gas can beset to suitable ranges for each narrow tube 60, even if the suitableranges for the composition and pressure of the discharge gas to obtain ahigh luminous efficiency and a long life are different for each of thethree colors of phosphor layer. Also, since the discharge startingvoltage can also be adjusted for each color, adjustment of the colortemperature is easily achieved.

Following is a description of examples-of settings for the compositionand pressure of the discharge gas.

A mixed gas of He and Xe, a mixed gas of Ne and Xe or the like may beused as discharge gases. Here, in the narrow tubes 60 including a redphosphor layer 61R, the fraction of Ne contained in the discharge gas isset high (a mixed gas of Ne and Xe containing 5% Xe by volume), in thenarrow tubes 60 including a green phosphor layer 61G, the fraction of Necontained in the discharge gas is reduced (a mixed gas of Ne and Xecontaining 10% Xe by volume) and, in the narrow tubes 60 including ablue phosphor layer 61B the fraction of Ne contained in the dischargegas is further reduced, and the fraction of Xe contained is furtherincreased (a mixed gas of Ne and Xe containing 15% Xe by volume).

For the narrow tubes 60 including a red phosphor layer in this way, byincreasing the quantity of contained neon, emission color from the redphosphor layer is enhanced by the red emission due to the neon, and bothan improvement in the color purity and an increased discharge efficiencyare possible. Meanwhile, for the narrow tube 60 including a bluephosphor layer 61B, by reducing the quantity of contained neon, redemission is suppressed and ultra violet light emission increased due tothe increased quantity of Xe, and an increase in emission from the bluephosphor layer 61B is therefore possible. Using these techniques, thecolor temperature when white is displayed can be increased.

Further, the narrow tubes 60 including red phosphor layers 61R and greenphosphor layers 61G may be filled with the discharge gas at a pressureof 400 Torr (53.2 kPa), and the narrow tubes 60 including the bluephosphor layers may be filled with the discharge gas at a pressure of500 Torr (66.5 kPa). Using this technique, emission from the bluephosphor layer can be increased, and hence the color temperature whenwhite is displayed can be increased.

Hence, a high definition PDP can be offered by adjusting, in this way,the pressures and compositions of the discharge gases filling the narrowtubes 60 according to type of phosphor layer included therein.

(PDP Manufacturing Method)

Phosphor Layer and MgO Layer Forming Process:

Glass tubes to be used as material for the narrow tubes 60 are prepared,phosphor application fluid (a fluid with dispersed binder and phosphor)is poured into the glass tubes, and the arrangement is dried with theaxes of the glass tubes held horizontal. By this method, phosphor inklayers are formed on the lower part of the inner surface of the narrowtubes 60, as shown in FIG. 5A. By firing this arrangement the phosphorlayers 61 are formed inside the narrow tubes 60. The dimensions of thenarrow tubes 60 are, for example, outside diameter 1.0 mm, insidediameter, 0.9 mm and length 130 cm.

Next, with the phosphor layer on the upper side as shown in FIG. 5B, MgOapplication fluid (a fluid with dispersed binder and MgO) is poured intothe narrow pipes, and the arrangement is dried with the glass tubes heldin a horizontal position. By firing this arrangement narrow glass tubeswith phosphor layers 61 and opposing MgO layers as shown in FIG. 5C areformed.

Note that though the order in which the MgO layers 62 and the phosphorlayers 61 are formed may be reversed, it is preferable to form thephosphor layers 61 first and the MgO layers 62 second as described aboveso as to avoid the phosphors adhering to the surface of the MgO layer62. Note also that after applying the phosphor application fluid anddrying the arrangement, the MgO fluid can be applied and dried withoutfirst firing the arrangement, in which case the phosphor and the MgOlayer are fired simultaneously.

The required number of narrow tubes 60 with a layer of red phosphor 61Rformed within, the required number of narrow tubes 60 with a layer ofgreen phosphor 61G formed within and the required number of narrow tubes60 with a layer of red phosphor 61B formed within are manufactured inthis way.

Discharge Gas Enclosing Process:

To enclose discharge gases of predetermined compositions atpredetermined pressures, the narrow tubes 60, each with a phosphor layer61 and an MgO layer 62 formed within, are collected into groups of eachcolor. Then, after being connected to a vacuum pump and evacuated, thenarrow tubes have discharge gases introduced internally and their endparts heat-sealed.

Data Electrode and Rib Forming Process:

The data electrodes 52 and the ribs 53 are formed on the substrate 51.The data electrodes 52 may be formed by applying a conductive paste in apattern and then firing the arrangement or, alternatively, by bondingaluminum-strings (narrow strips of aluminum foil) onto the substrate 51.The ribs 53 are formed by applying a glass material or a resin in apattern, and then curing the arrangement.

Note that the order in which the data electrodes and the ribs are formedis not important; either process may take precedence.

Note also that the ribs 53 are not strictly necessary, but forming theribs makes it easier to align the narrow tubes.

Narrow Tube Aligning Process:

The narrow tubes 60 enclosing the discharge gases are arrayed on thesubstrate 51. Here, ribs 53 have been formed on the substrate 51 and soarraying is easily achieved by disposing the narrow tubes 60 in thegrooves 54 between the ribs. Then, a bonding layer 63 is formed byapplying a bonding agent in the gaps between the aligned narrow tubes60. The aligned narrow tubes 60 immobilize each other via the bondinglayer 63.

Discharge Electrode Forming Process:

Discharge electrodes 71 a and 71 b are disposed on top of the arrayednarrow tubes 60.

The discharge electrodes 71 a and 71 b may be formed by sticking downaluminum-strings (narrow strips of aluminum foil), or by applying aconductive paste in a pattern and then firing the arrangement.

Since the surfaces of the narrow tubes 60 are curved, it is difficult toform electrodes having a uniform width when a method such as screenprinting or photolithography is used to apply conducting paste in apattern. However, when an aluminum-string sticking method or a nozzlescanning method in which a nozzle scans along the surface of the arrayednarrow tubes 60 is used, electrodes of a uniform width can be formed

Effects According to the Manufacturing Method of the Present Embodiment

According to the manufacturing method of this embodiment, narrow tubes60, which have the phosphor layers 61 formed within, have two or moredischarge gases enclosed and are then arrayed on the substrate 51.Hence, for each narrow tube 60, the pressure and the composition of thedischarge gas to be enclosed can easily be adjusted. Moreover, unlikethe Embodiment 1, there is no need for a process to combine the twopanels in an airtight manner.

Example Modifications to the First and Second Embodiments

Although in the Second Embodiment only one substrate is used, a secondsubstrate may be provided on top of the arrayed plurality of narrowtubes 60 on the substrate 51, sandwiching the plurality of narrow tubes60 between the two substrates. In such a case, the discharge electrodes71 a and 71 b may be formed on the second substrate.

In the PDP described in the Second Embodiment, phosphor layers areprovided on the inside surface of the narrow tubes 60. However, insteadof phosphor layers on the inside surface of the tubes, light emittingmaterials of each color, which excitedly emit red, green and blue lightunder ultraviolet light, may be added to the glass material that formsthe narrow tubes 60. Some possible examples for the light emittingmaterials of each color are Eu₂O₃ for the red light emitting material,Tb₂O₃ for the green light emitting material, and EuF₂ for the blue lightemitting material.

In the Second Embodiment, since the end parts of each narrow tube 60 aresealed, the narrow tubes 60 including the red phosphor layers 61R, thenarrow tubes 60 including the green phosphor layer 61G and the narrowtubes 60 including the blue phosphor layer 61B are all independent ofone another. However, narrow tubes 60 containing any two of the phosphorlayers may be connected, in which case the composition and pressure ofthe gas in contact with the phosphor layers of the two colors is thesame. Where, for example, the narrow tubes 60 including the red phosphorlayer are connected to the narrow tubes 60 containing the green phosphorlayer, the internal space is divided in substantially the same way asfor Example 1 above; where the narrow tubes 60 including the greenphosphor layer are connected to the narrow tubes 60 including the bluephosphor layer, the internal space is divided in substantially the sameway as for Example 2 above; and where the narrow tubes 60 including thered phosphor layer are connected to the narrow tubes 60 including theblue phosphor layer, the internal space is divided in substantially thesame way as for Example 3 above.

In the First and Second Embodiments, the pressure at which the dischargegas is enclosed may be less than atmospheric pressure or greater thanatmospheric pressure. Also, each discharge electrode may be divided intoa plurality of narrow lines. In such a case, each line electrode may beformed using aluminum wire.

In the First and Second Embodiments, a PDP having phosphor layers of thethree colors, red, green and blue is described, but the presentinvention may be implemented on any PDP having phosphor layers of two ormore colors in a similar way.

In the First and Second Embodiments, the directions of the dischargeelectrodes and the data electrodes may be reversed, the dischargeelectrodes being provided in the direction in which the phosphor layersof each color extend, and the data electrodes being provided in adirection at right angles to the discharge electrodes.

In the First and Second Embodiments, a surface discharge PDP isdescribed, but a similar implementation is possible in an opposingdischarge type of PDP. Furthermore, the present invention may be widelyapplied to any image display device that includes a plurality ofphosphor types in an internal space in which a discharge gas isenclosed.

INDUSTRIAL APPLICABILITY

The present invention may be utilized in computer and television imagedisplay apparatus, for example, especially in large type image displayapparatus.

According to the present invention, since superior color emission can beobtained and the lifetime of the phosphor layers can be extended, a highdefinition image display apparatus can be provided

1. An image display apparatus in which a pair of substrates are disposedopposite one another such that an internal space is formed therebetween,electrodes and at least two types of phosphor layer are provided betweenthe substrates, and discharge gas is enclosed in the internal space, theimage display apparatus displaying an image by applying voltages to theelectrodes so as to cause discharges to occur in the internal space, andvia the phosphor material, converting ultraviolet light generated asdischarges occur into visible light, comprising: the internal space ispartitioned by a plurality of barrier ribs in a stripe pattern whichform a plurality of grooves, and among the grooves, (a) groovesconstituting a first space are closed at one end by auxiliary barrierribs and connect with one another at an other end and (b) groovesconstituting a second space are closed at the other end by auxiliarybarrier ribs and connect with one another at the one end such that (i)the internal space is divided into the first space provided with a firstphosphor layer and the second space provided with a second phosphorlayer and (ii) the grooves constituting the first space connect with oneanother and the grooves constituting the second space connect with oneanother, and the discharge gases respectively enclosed in the first andsecond spaces differ from each other in at least one of composition andpressure.
 2. The image display apparatus of claim 1, wherein, the firstphosphor layer is of at least one color selected from red, green andblue, and the second phosphor layer is of at least one color other thanthe at least one color selected for the first phosphor layer.
 3. Theimage display apparatus of claim 1 wherein the image display apparatusis a plasma display television set with a plurality of pairs ofdischarge electrodes arranged on a facing surface of a first substrateof the pair of substrates.
 4. An image display apparatus manufacturingmethod comprising: an outer vessel forming step of forming an outervessel in which pair of substrates are disposed opposite one anothersuch that an internal space is formed therebetween; electrodes and atleast two types of phosphor layer are provided between the substrates;discharge gas is enclosed in the internal space, the internal space isprovided with a first phosphor layer and a second space provided with asecond phosphor layer, and partitioned by a plurality of barrier ribs ina stripe pattern which form a plurality of grooves, and among thegrooves, (a) grooves constituting a first space are closed at one end byauxiliary barrier ribs and connect with one another at an other end and(b) grooves constituting a second space are closed at the other end byauxiliary barrier ribs and connect with one another at the one end suchthat (i) the internal space is divided into the first space providedwith a first phosphor layer and the second space provided with a secondphosphor layer and (ii) the grooves constituting the first space connectwith one another and the grooves constituting the second space connectwith one another, first and second exhaust tubes connecting to the firstand second spaces respectively are provided; and an exhausting-enclosingstep of, via the first and second exhaust tubes respectively, exhaustingthe first and second spaces and enclosing discharge gas therein,wherein, in the exhausting-enclosing step, the discharge gasesrespectively enclosed in the first and second spaces differ from eachother in at least one of composition and pressure.
 5. The image displaymanufacturing method of claim 4, wherein, the first phosphor layer is ofat least one color selected from red, green and blue, and the secondphosphor layer is of at least one color other than the at least onecolor selected for the first phosphor layer.